Motor-control system



June 10, 1924. 1,497,448

H. KEITH MOTOR CONTROL SYSTEM Filed Feb. 15, 1919 2 Sheets-Sheet 1WITNESSES: 7 INVENTOR w I BY ATTORNEY June 10, 1924. 1,497,448

H. KEITH MOTOR CONTROL SYSTEM Filed Feb. 15, 1919 2 Sheets-Sheet 2 T73 vT/J WITNESSES: INVENTOR 754.7% Ham/d L. Half/7 ATTORNEY Patented June'10, 1924.

UNITED STATES PATENT OFFICE.

HAROLD L. KEITH, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WB'IINGHOUEEELECTRIC do MANUFACTURING COMPANY, A CORPORATION 01' PENNSYLVANIA.

MOTOR-CONTROL SYSTEH.

Application filed February 15, 1919. Serial No. 277,147.

I To all whom iii-may concern:

' produce different numbers of field-ma Be it known that I, HAROLD L.KEITH, a. citizen of the United States, and a resident of Wilkinsburg,in the county of- Allegheny and State of Pennsylvan1a,'have invented anew and useful Im rovement in Motor-Control S stems, of w 'ch thefollowing is a'speci cation.

My invention relates to motor-control.

systems and articularly to such systems as are employ in connection withelevators, hoists'and similar machines. I

In my co ding application, Serial No. 100,251, fil May 27,1916, I havedisclosed a motor-control. system with the aid of in the number of polesproduced by them,

to their res tive rimary windings. The terminals 0 each oi the secondarywindings are connected to variable resistors through a single set ofslip rings.

The resistors are in circuit with the secondary winding that isenergized when the low-speed primary winding is connected in circuit tostart the motor. The resistor is then gradually and automaticallyshunted by electroma etic switches to cause the motor to reach itsnormal speed with the lows dwinding in circuit. The circuit of t elow-speed winding is broken, the high-' speei winding is connected incircuit and the resistor is, at the same time, in insorted into thesecondary ci'rcuit.' e resistor is gradually shunted, as before, toaccelerate the motor to its normal operating speed with the high-speedwinding in circuit.

The low-speed connections are established when a two position controlleroccupies one of its positions and the high-speed connections when thecontroller occupies its other ,fer relay position. The high-speedconnections cannot be established, however, until after the operation ofa current-limit relay which is mechanically connected to each of thereversin switches.

If t e controller should he pen to be actuated quickly to' itsfullposition, the

current-limit relay, particularly if the motor is operating underarheavy load, mi ht close too soon; either directly upon the c osing ofthe reversing switch or at a time previous to the short circuiting ofthe entire resistor during low-speed operation. In

either event, the result would be a prema."

ent invention is to insure the initial operation of the motor at lowspeed and the subsequent operation at high speedonly after the resistorhas first been entirely shortcircuited during the period of low-speedoperation.

I effect this result, in the embodiment of my invention which is hereshown, by dis"- pensing altogether with the abov -mentionedcurrent-limit relays. I control the energization of the transfer-relaycoil by a current-limit relay which is mechanically connected to thelast accelerating switch to operate. This coil is therefore energized ata predetermined time after, and not before, this accelerating switch isclosed. As the accelerating switches are immediately thereupon reopenedto reinsert the resistor into circuit preparato? to high-speed o ration,I provide means or maintaining t e transclosed independentl of themechanical y-connected relay. T e transfer of connections is thusefi'ected at the exact moment required, the operation is more positivein its action and the apparatus is cheaper, because requiring a smallernumber of parts. I

My invention will be described in connection with the accompanyingdrawin in which Fig. 1 is a diagrammatic view 0 the main circuits andapparatus embodying my sired or lowspeed double-pole electro naconnected to the swi which will appear hereinafter. The relay 49 tionedbelow, for the purpose of establishin re lacement is less advanta eons,as

pointed out later. A switc 56 is mechsnie invention. Fig. 2 is a similarview of the control circuits. Fig. 3 is a diagrammatic representation ofthe seconda circuits of the motor shown in Fig. 1. 4 illustrates aschematic arrangement 0 the connection of the source to the primarywindings of the motor. It will be noted that the main circuits andcontrol circuits have been lllustrated in separate views for the sake ofas. 1|: Referring particularly to Fig. 1, line conductors 1, 2 and 3,which may be connected to any suitable source of alternating cur rent,supply ener to an alternating-current motor 4 whic primary windingswound 'for ei ht poles and twent -four poles, respective y, as indies.by the accompanying legends. It will be understood that the numbers ofpoles produced by the prima windings are taken y way of example 0 y andthat any deratio may exist between the m;- of poles produced by therespective wind shown in Fig. 3, the secondary member of the motor 4 isrovided with base windings 6 and 6 whic are respective y arranged toproduce eight poles and twenty-four poles coponding to the primarywindiiigs. The

1: 1- 5 and 6, which are in para el relation, a connectedto a sin 1e setof col lector rings-7. Three varia le resistors 8,

,the actuating coil of switch 12 which con- "trols the circuitconnections of which are respectively connected to the coll lector mi 5and 6;

Befierring in to Fig. 1, the rimary circuits of the motor are controllually switches and 11 which determine the direction of operation of themotor 4 when eithercf the prilna? i icuit. circuits 0 v thetwenty-four-pole winding are controlled by a etic switch 12, and thecircuits-of the eig t-pole or high-speed in; are controlled by a similarelectron=,' 8t0 switch 13. One terminal of each i primary wind isconnected to line conductor 2 directly through switch 9. The resistors 8are shunted during the normal operation of the motor by a series ofproively operable electrognetic switches 14, end 16. A rela 49 ismechanically 16- for a purpose may, it desire be replaced by a switchrigid- I connected to the switch 16, so as to c ose e circuit-which itcontrols simultaneously with the operation of the switch 16, blgiifilhtically connected to a transfer relay 20, mena mainta circuit for theactuatingflco of thi s r elay independently of the relay is providedwith two fl 7, are in circuit with each of the by a man operable switch'9 and reversingerator26thrbugh hatchway limit by the relay 49simultaneously with t e energization'of.

the coil 50.

Reference may which thecontrol circuits are dia call illustrated. Amaster switc now be had to Fig. 2,-in

ammatior contro er 18, which may be located Within the elevator car,controls the circuitsof actuating coils of the several switches forcontrolling the main circuits described above in connection with Fig. 1.The actuatin mil of each of the accelerating switches 14, 15 and 16 iscontrolled by a current-limit .relay that is connected to the precedingswitch to close. While the relays may be connected,

in any suitable manner, to the respective switches, they are, forconvenience, repre- 35 sented as being normally held open by s} springs19. The pressure of the springs 19 is released by a lever arm 21 whenthe corresponding accelerating switch is cl,

thereby permitting the relays to close by gravity except when theiractuating coils are 7 traversed by determined value.

a current which exceeds a pre- The controller 18 has two operativepositions, in one of which it comp for the actuating coil of the one orthe other of the reversing switches 10 and 11 and for the system ofinabove mentioned a plication, this circuit is also controlled by ecurrent limit relays connected to. 'reve mg switches 10 and 11. Thesecurrent limit reetes a circuit are omitted from the present system.

Th transfer relay 20 operates to open the circuit of the magnet coil ofswitch 12 and to efiect the closing of switch 13 and thereby change thenumber of poles produced-in the primary member of the motor. 7 Y It maybe assumed that the various switches are in their illustrated orinoperative ositions; The circuits of the primary win ings of the motorare 0 n, and the resistors 8 are in circuit with t e seconds windings ofthe motor It may be m. further, that it is desired to cause thejelevator car to ascend. The operating handle of the master switch 18 isrotated in a clockwise direction, as viewed in Fig. 2, to cause movablecontact cuts 22 and 23 to. enmi,

gage stationary contact members 24 and 25,,

: ctively.

. rrcuit is completed which extends from the positiye terminal of adirect-current genswitches 27, emergency switch 28, "actuating coils 29and 30 of brake-controlling switches 32 and 33, actuating coil 34 ofswitch 10, hatchway limit switch 47, contact member 25, contact segment23, and contact member 35, to the negative terminal of the generator 26.The

circuits of the magnet coils 37 and 38 of the usual electromagneticbrakes (notshown) and thus effect the release of the brakes.

The coil 34 is energized by the circuit first traced to close reversingswitch 10 in order to insure that the motor 4 will operate in the properdirection. The coil 36 is energized, also, by the second circuit toclose line switch 12 and thereby complete the circuit of the twenty-fourpole or low-speed winding of the motor.

At the time of starting the motor, the current traversing the secondarycircuit comprising the twent-y-four-pole secondary winding, theresistors 8 and coils 39 of the current-limit relays, respectivelyconnected to switches 12 and 13, is of such value that the current-limitrelay 40, which is connected to the switch 12, is held in its openposition. The relay 40 controls the circuit of the actuating coil 41 ofaccelerating switch 14.

When the current traversing the secondary circuit falls to apredetermined value, the relay 40 closes to complete a circuit for thecoil 41, and the switch 14 is closed to complete a shunt for one sectionof each of the resistors 8. A current-limit relay 42, that ismechanically connected to accelerating switch 14, controls the circuitof the actuating coil 43 of switch 15, and the latter switch is closedto shunt a second section of. each resistor 8 when the currenttraversing the secondary circuit again fails to the predetermined value.In a similar manner, switch 16, which is provided with an actuating coil44 that is controlled by a currentlimit relay 46 connected to switch 15,operates automatically in accordance with the value of the currenttraversing the secondary circuit to complete shunt circuits for theentire resistors 8.

The removal of the. resistors from the secondary circuit graduallyaccelerates the motor to its normal speed, with the twenty- ;iour-polewinding in circuit. When the controller is actuated to its secondposition, the contact segment 23 engages a contact member 48 butmaintains its enga ement with contact members 25 and 35. he currentlimitrelay 49, that is connected to the accelerating switch 16, closes tocomplete a circuit for the actuating coil 50 of transfer relay 20 whenthe current traversing the secondary circuit falls to a predeterminedvalue.

This circuit extends from the positive terminal of the enerator 26,through hatchway limit switches 27, emergenc switch 28, the relay 49,coil 50, a hatchway limit switch 57, contact member 48, contact segment23 and contact member 35 to the negative terminal of the generator. Thecoil 50 is energized to actuate the transfer relay 20 to its upperposition to open the circuit of the actuating coil 36 of line switch 12and to close a circuit for the actuating coil 51 of line switch 13. Thiscircuit extends from the relay 20, which is connected to the positiveterminal of the generator 26, through coil 51 and swith 33 to thenegative terminal of the generator.

The line switch 12 opens the circuit of the twenty four-pole winding,and an interlock 52, that is connected thereto, opens to break thecircuits of the coils 41, 43 and 44 of the corresponding acceleratingswitches 14, 15 and 16. The entire resistors 8 are thus inserted incircuit with the secondary windings of the motor. The coil 50 ismaintained energized, upon the opening of its circuit by the switch 49,by the switch 56.

The line switch 13 closes to complete the circuit of the eight-pole orhigh-speed winding. The eight-pole seconds. winding is now energized andsubstantial no current traverses the twenty-four poll; secondary windingbecause the various electromotive forces impressed upon its conductorsare substantially equal and in opposite directions. An interlock 53,that is connected to the switch 13, again completes the circuit ofactuating coil 41 of accelerating switch 14 when the currentdimit relay54, connected to the line switch 13, closes in response to a decrease inthe current traversing the secondary circuit to a predetermined value.The accelerating switches operate automatically in the same manner asdescribed above in connection with the low-speed winding to acceleratethe motor to its normal operating speed, with the high-speed windingconnected in circuit.

The operation of accelerating the motor has been described upon theassumption that the controller is operated step-by'step in ac: cordancewith the speed of the motor. It will be understood, however, that thecontroller handle may be actuated quickly from its off position to itsfull-speed position, and the various switches will operateautocelerating switch to close. The accelerating" switches operateautomatically upon the current traversing the secondary circuit fallingto predetermined values and are caused to repeat their operation whenone line switch is opened and the other is closedby the oporation of thetransfer relay. The operation of the motor, first at one speed and thenat the other, is thus assured.

To decreasethe speed of the motor, the operating handle may be actuatedtoward its inoperative position. \Vhen it occupies its intermediateposition, the circuit of the coii'50 of relay 20 is broken at contactmember 48. The transfer relay 20 falls to its lower position to openthecircuit of the actuating coil '51 of line switch 13 and to establish thecircuit for actuating coil 36 of line switch 12. The in terlock 53,opens the circuits of the actuating coils of the accelerating switchesto insert the resistors 8 in the secondary circuit. The circuit of coil$1 of switch 14 is again established by the interlock 52 connected'toline switch 12. The accelerating switches close in order as the currenttraversing the secondary circuit falls to predetermined values. If thesecondary current does not rise to the predetermined value at which therelays 40. 42 and 46 are held open, the switches close immediately. I

At'the instant the change in connections from the eight-pole'primarywinding to the twenty-four pole winding occurs, the motor is operatingabove the synchronous speed for this connection. As an induction motordriven above synchronous speed operates as a generator, an electricalbraking action is provided which quickly retards the motor and theelevator car. The insertion of the resistors in the secondary circuitduring the change in connections andthe step-by-step removal of theresistors eflect a gradual reduction from the higher synchronous speedto the lower synchronous speed. The speed of the car may thus be quicklyreduced from, for example, 300 feet to 100 feet per minute without shockor jar, from which speedaccurate stops are easily made.

To stop the motor, the controller is actuated to its ofi position. Thecontrol circuits are thus opened, and the motor is disconnected from theline. The switches 32 and 33 open'the circuits of the brake coils 37 and38 to permit the application of the The .car is thusbrought' magnetbrakes. easily and smoothly to rest. The opening of theco'ntrolvcircuits efiects'the opening of the accelerating switches, and the'resistors are inserted in the secondary circuit in preparation for thesucceeding operation of the motor.

To cause the motor to rotate in the opposite direction to lower theelevator car, it is only necessary to act ate the controller handle inthe opposite direction from its ofi position to efi'ect the closing ofreversing switch 11 which is provided with an actuating coil 55. ationsis otherwise the same as previously described in connection with theascent of the car. In case the operator neglects to The sequence ofoper-- stop the motor before the car reaches either p of its limits oftravel, the hatchway limit switches 57 and 47 may be successively openedby any usual or suitable mechanical means controlled by the car to openthe control circuits in the same sequenceas if the controller handlewere thrown to its ofi position. The car is thus automatically andgradually brought to a stop. In case it is impossible to stop the car bymeans of the master switch 18, it is only necessary to open the'manuallyoperable emergency switch 28, or the hatchway limit switches 27 willopen in case of overtravel (both sides of the control circuit beingopened to guard against grounds or short-circuit), whereupon, all of thecontrol circuits are de-energized and the car is brought to rest uponthe opening of all of the main and control switches and the applicationof the brakes- As stated above, a switch may be substituted for therelay 49 that shall close simultaneously with the switch '16. The relay49, however, permits the motor to reach full' speed while operating onthe twenty-four pole winding before the transfer of connecthe variousfeatures are shown by way ofv example only, and that any other suitablearrangement may be substituted therefor. The control circultsare shownand described as being controlled bymeans of direct current, but it willbe obvious that alternating current may be employed by providingelectromagnets of a'character suitable for'such use. Many'modificationswill occur to those skilled in the art to which my invention appertains,and it is understood that such changes--maybe made as fall within thescope ot-"thaappended claims withoutdeparting from the spirit of myinvention.

, I claim asmy invention:

1. The-combination with an electric motor having a plurality of primarywindings, a resistor associated with said motor and means forshort-circuiting said resistor, of means for rendering the one or theother of said windings effective to produce a plurality of operatingspeeds, and an electroresponsive switch mechanically connected to saidshort-circuiting means for controlling the electrical connections of oneof said windings.

2. The combination with a two-speed alternating-current electric motorhaving a resistor associated therewith and a switch for short-circuitingsaid resistor, of means for insuring the initial operation of said motorat the lower speed, said means comprising an electromagnetic switchmechanically connected to said short-circuiting switch for effecting theoperation of said motor at the second and higher speed.

3. The combination with a motor having a resistor associated therewith,a switch for short-circuiting said resistor and a two-positioncontroller for arranging the motor connections to effect the operationof said motor at each of two speeds and to effect the acceleration ofsaid motor in each of its two positions, respectively, of acurrent-limit relay mechanically connected" to said shortcircuitingswitch. for controlling the motor connections for operation at one ofsaid speeds.

4. The combination with an electric motor having a primary memberadapted to produce difierent numbers of poles and a secondary memberhavin a resistor in circuit therewith, of a pair 0 switches forconnecting said primary member to produce one or another of said numbersof poles, a transfer switch for rendering one of said pair of switchesineffective and the other of said pair of switches effective, a switchfor shortcircuiting said resistor and a current-limit relay mechanicallyconnected to said shortcircuiting switch for controlling said transferswitch.

5. The combination with an electric motor having a primary memberadapted to produce difi'erent numbers of poles and a secondary memberhavin a resistor in circuit therewith, of a pair of switches forconnecting said primary member to produce one or another of said numbersof poles, a transfer switch for rendering one of said pair of switchesineffective and the other of said pair of switches effective, saidtransfer switch having an actuating coil, a switch for short-circuitingsaid resistor, a current-limit relay mechanically connected to saidshortcircuiting switch for closing the circuit of said coil and a switchfor maintaining said first-named coil energized.

6. The combination with an electric motor having a primary memberadapted to produce different numbers of poles and a secondary memberhaving a resistor in circuit therewith, of a pair of switches forconnecting said primary member to produce one or another of said numbersof poles, each having an actuating coil, a transfer switch having twooperative positions in each of which it controls the circuit of one ofsaid coils, said transfer switch normally occupying one of saidpositions and having an energizing coil for actuating it to said otherposition, a plurality of progressively actuated switches forshort-circuiting said resistor, and a current-limit relay mechanicallconnected to the last of said progressively actuated switches to operatefor closing the circuit of said transfer-switch coil.

7 The combination with an alternatingcurrent motor having a low-speedand a high-speed primary winding, and a secondary winding, of means foraccelerating the motor when its low-speed winding is effective and meanscontrolled by said aocelerating means and in accordance with the valueof the current traversing the secondary winding, for rendering thehigh-speed winding effective and.the low-speed windin inefl'ective.

n testimony whereof I have hereunto subscribed my name this 31st day ofJan.,

HAROLD L. KEITH.

